Postganglionic Nerve Fibers - Neurotransmitters

Neurotransmitters

The neurotransmitters of postganglionic fibers differ:

• In the parasympathetic division, neurons are cholinergic (that is, acetylcholine is the primary neurotransmitter.)

• In the sympathetic division, neurons are mostly adrenergic (that is, epinephrine and norepinephrine function as the primary neurotransmitters.) One exception to this rule is the sympathetic innervation of sweat glands, where acetylcholine is the neurotransmitter at both pre and post ganglionic synapses. Another exception is the sympathetic innervation of the medulla of the adrenal glands, which is accomplished by preganglionic fibers, and subsequently uses acetylcholine as a neurotransmitter. The cells of the adrenal medulla are actually modified postganglionic neurons which secrete epinephrine and norepinephrine directly into the blood stream rather than into a synapse.